I first made a post on this back in July. Since then I've thought of more to add to it. A recent conversation with fellow blogger Iapetes (who needs to post more) made me realize that manipulation of time could potentially affect anything, but especially in the areas of buffs and debuffs. This would be primarily a support class, though it would be capable of soloing.
Any time I give a duration or cooldown, don't take it as an absolute. They're just to give general ideas of "this is a short duration" or "this has a long cooldown."
Damage mitigation and healing
Imagine someone just got hit with 20k damage and died. Maybe it's a warrior on 3D Sarth or just the latest bad mechanic to encourage stam-stacking. Chronomancers would have various ways to deal with this.
Rewind: Chronomancers could, on a cooldown, reverse a fight by 10 seconds, allowing a raid to say "ooh, a bad thing will happen now, tank, pop shield wall this time."
Undo: The last attack didn't happen. This wouldn't undo death, but would act as a powerful heal.
Skip Ahead: Go back to a couple seconds before someone died and bring them to now. Think of it as a combat res with the added convenience of not requiring rebuffing. However debuffs remain, so someone will need to watch that cleanse button.
Time Mirror: Reverse the flow of time for a single spell. This is a proactive version of Undo, being used before the attack (spells only), which will cause it to cast backwards, damaging the caster. Think of spell reflect usable on a specific group member.
Obviously haste would be a standard buff.
Fast Forward: The next ten seconds are recorded and then repeated when the recording is over. This is their Bloodlust, but potentially much more powerful. Use this with every single cooldown you can imagine because it acts as 200% DPS for 10 seconds. There is a big risk though: it also records damage and healing on players, so if your tank isn't being kept topped off properly, he may be dead after the Fast Forward, along with anyone standing in a fire or anything else bad. This would have a sufficiently long cooldown to be unusable in arenas.
Generic single-target haste buff: Attack or cast faster.
Simpler Times: Delevel an ally, reducing all base stats. This is bad right? Well, not exactly. Throw it on a caster and when their base mana drops, so do their spell costs. The efficiency gain will offset the slightly lower stats.
Remember the Good Times: Grants the Nostalgia buff, making the target immune to fear effects.
It's Time: Resets all cooldowns on friendly players.
Show Death: Show the target when and how they will die, fearing them.
Delevel: Lower the target's level, but rather than affecting stats, it affects the hit table. This acts as both a damage reduction for them due to higher relative miss, crit, etc. and a damage buff for the group due to the opposite.
Premature Aging: The target ages rapidly, snaring it and reducing all stats derived from agility: dodge, crit, and armor.
Freeze Time: All enemies are frozen for 4 seconds, making them immune to all damage and unable to attack. If there are multiple Chronomancers in combat (or even out of combat if its arena), the spell will last for 4 seconds for each Chronomancer. Chronomancers are immune to time stop.
See You Later: Moves the target into the future, making them unable to attack or take damage for 6 seconds. This can also be used on allies and could be helpful for things such as surviving a large AoE when at low health.
Teamwork: Summons a future and past self to fight with the caster for 20 seconds. If the past self dies, the caster dies. In addition, the present and future selves are weakened by having too many selves at the same time. However both selves are hard to damage, frequently using most known abilities, especially Time Mirror. The benefit is more damage, but at an elevated risk of death since you now have two ways to die.
Get It Over With: Accelerates the speed at which a CC ends. It will not remove the CC, but it can turn a full fear into only a second or two.
Save: The Chronomancer can save a time and if desired, bring the raid back to that time. Think of it as a convenience spell: save before a boss fight and you won't have to run back after a wipe, save after the long rant at the start and you skip that next time. Or use it to reduce risk: save before a phase transition that you're still learning and then you won't need to repeat previous phases and risk earlier deaths.
Past Situation: This would be the primary nuke. It would work by grabbing energy from way the past and throwing it at enemies. The damage time is random and the value will vary more than a normal spell cast. This is because the caster just grabs whatever is going on at the time rather than searching around for the most destructive damage. This could also be used to grab enemy attacks from earlier in the fight and throw them back, so Chronomancer damage types would depend greatly on luck and the mob they're fighting.
For resources, I think an energy bar would work best. I don't want any scaling regen mechanic since the abilities are far too powerful to spam.